1. Field of the Invention
The invention pertains to the field of engine lubricating systems. More particularly, the invention pertains to a method of providing hydraulic pressure for mechanical work from an engine lubricating system.
2. Description of Related Art
Conventionally, accessories in cars (e.g. cooling fan, power steering system, A/C compressor, engine coolant pump, supercharger, and alternator) are powered using separate engine driven, fixed displacement pumps, or by direct drive, where the individual power demands of the accessories are not well matched to engine speed.
Solutions to the allocation of power by accessories are shown in U.S. Pat. No. 3,952,509, U.S. Pat. No. 4,420,937, U.S. Pat. No. 4,819,430, U.S. Pat. No. 5,800,131 and U.S. Pat. No. 6,644,025.
In U.S. Pat. No. 3,952,509 a variable displacement pump supplies hydraulic fluid to continuous and intermittent output hydraulic circuits. The continuous circuit supplies pressure for the power steering in a tractor, and the intermittent circuit provides pressure for activating hydraulic rams, for example, for moving an auger up and down. A first flow divider provides constant pressure to the continuous hydraulic circuit. A second flow divider provides pressure if any of the hydraulic cylinders in the intermittent hydraulic circuit are actuated. The loads on the system are for hydraulic pistons and not continuous flow devices, such as motors, and the system does not provide engine lubrication.
U.S. Pat. No. 4,420,937 discloses a system where the displacement of a variable displacement pump in a hydraulic circuit is at a minimum when the actuators in the system are not operating. The circuit includes a flow sensor that detects the dynamic pressure of a fluid and can covert static pressure to dynamic pressure.
U.S. Pat. No. 4,819,430 discloses a hydraulic fluid circuit that is divided into two circuits, a first circuit and a second circuit. A variable displacement pump is the fluid source for the first circuit for regulating the steering system. The second circuit is controlled by a fixed displacement pump. A valve responsive to the demands between the first circuit and the second circuit increases the amount of output from the fixed pump into the first circuit in proportion to the output of the variable displacement pump.
U.S. Pat. No. 5,800,131 discloses a variable displacement pump regulating engine lubricating oil flow based on engine parameters. Oil pressure is used to move a piston.
U.S. Pat. No. 6,644,025 discloses a control arrangement that supplies pressurized hydraulic fluid to at least two hydraulic devices. The control arrangement includes a variable displacement pump, which is controlled according to required flow and settings and pressure compensators. This control arrangement prevents excess flow of hydraulic fluid to the hydraulic devices by using the pressure compensators and allowing only one valve device to derive the control pressure from the feed pressure.